hessian writes: "This bizarre finding—christened the “Flynn effect” by Richard Herrnstein and Charles Murray in The Bell Curve—has since snowballed so much supporting evidence that in 2007 Malcolm Gladwell declared in The New Yorker that “the Flynn effect has moved from theory to fact.” But researchers still cannot agree on why scores are going up. Are we are simply getting better at taking tests? Are the tests themselves a poor measure of intelligence? Or do rising IQ scores really mean we are getting smarter?

In spite of his new book’s title, Flynn does not suggest a simple yes or no to this last question. It turns out that the greatest gains have taken place in subtests that measure abstract reasoning and pattern recognition, while subtests that depend more on previous knowledge show the lowest score increases. This imbalance may not reflect an increase in general intelligence, Flynn argues, but a shift in particular habits of mind. The question is not, why are we getting smarter, but the much less catchy, why are we getting better at abstract reasoning and little else?"